Bitcoin (BTC) is a digital currency that enables peer-to-peer transactions aimed at functioning as a medium of exchange independent of any central authority. BTC can be transferred electronically in a secure, verifiable, and immutable manner.

BTC was launched in 2009 and is the first virtual currency to solve the double-spending problem by timestamping transactions before broadcasting them to all nodes in the Bitcoin network. The Bitcoin protocol provided a solution to the Byzantine Generals' problem through the blockchain network structure, a concept first devised by Stuart Haber and W. Scott Stornetta in 1991.

The Bitcoin whitepaper was published in 2008 by an individual or group using the pseudonym "Satoshi Nakamoto," whose true identity has yet to be verified.

The Bitcoin protocol uses a proof-of-work (PoW) algorithm based on SHA-256d to achieve network consensus. Its target block creation time is 10 minutes, and the maximum supply is 21 million tokens, with a decreasing issuance rate. To prevent fluctuations in block creation time, the network block difficulty is adjusted through an algorithm based on the previous block creation times over the past 2016 blocks.

With a maximum block size of 1 megabyte, the Bitcoin protocol supports both the Lightning Network, which is a second-layer infrastructure for payment channels, and the segregated witness, which is a protocol upgrade to increase the number of transactions in the block.